1. Field of the Invention
The present invention relates to an ink jet printing apparatus, and particularly to an ink jet printing apparatus which can change the diameter of a dot.
2. Description of the Related Art
This application is based on Japanese Patent Application No. 9-050574 filed in Japan, the contents of which is hereby incorporated by reference.
An ink jet printer (ink jet printing apparatus) has been known which changes the diameter of a dot to be printed by controlling the amount of ink emitted from a nozzle.
However, such an ink jet printer has problems as below.
(1) First Problem
Even if the same amount of ink is emitted, the diameter of a dot to be printed becomes large or small depending on the type of sheet on which printing is done.
(2) Second Problem
If printing is done on an OHP film, for example, much time is required for ink to dry compared with the normal type of paper. The conventional printer prunes dots to be printed in order to quickly dry the ink in such a case.
In order to carry out the process of pruning dots, the printer needs its own process of changing threshold value in error diffusion process or of pruning dots in a solid image (including characters). If the dither method is employed, separate look up tables are required for a case of pruning dots and a case of not pruning dots.
The necessity for the printer to have its own process for pruning dots in an image results in a complicated printing process done by an ink jet printer.
The present invention is made to solve such problems. The first object of the invention is to provide an ink jet printing apparatus which prints dots having an almost constant diameter regardless of the type of sheet to be printed.
The second object of the invention is to provide an ink jet printing apparatus which can speed up drying of ink adhering to a sheet by a simple process.
In order to achieve the objects above, an ink jet printing apparatus according to one aspect of the invention that can control an amount of ink emitted from a nozzle includes; a determining unit for determining readiness of drying of ink on recording media; and a controller which controls an amount of ink emitted from the nozzle by converting gradient of image data based on the determined readiness of drying of ink.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.